On Wed, 15 May 2024, Patrick Palka wrote:
>
> On Fri, 10 May 2024, Seyed Sajad Kahani wrote:
>
> > This patch resolves PR114915 by replacing the logic that fills in the
> > missing levels in do_auto_deduction in cp/pt.cc.
> > The new approach now trims targs if the depth of targs is deeper than
> > desired (this will only happen in specific contexts), and still fills targs
> > with empty layers if it has fewer depths than expected.
>
> The logic looks good to me, thanks! Note that as per
> https://gcc.gnu.org/contribute.html patches need a ChangeLog entry in
> the commit message, for example let's use:
>
> PR c++/114915
>
> gcc/cp/ChangeLog:
>
> * pt.cc (do_auto_deduction): Handle excess outer template
> arguments during constrained auto satisfaction.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp2a/concepts-placeholder14.C: New test.
> * g++.dg/cpp2a/concepts-placeholder15.C: New test.
> * g++.dg/cpp2a/concepts-placeholder16.C: New test.
>
> Jason, what do you think?
... now sent to the correct email, sorry for the spam
>
> > ---
> > gcc/cp/pt.cc | 20 ++++++++---
> > .../g++.dg/cpp2a/concepts-placeholder14.C | 19 +++++++++++
> > .../g++.dg/cpp2a/concepts-placeholder15.C | 15 +++++++++
> > .../g++.dg/cpp2a/concepts-placeholder16.C | 33 +++++++++++++++++++
> > 4 files changed, 83 insertions(+), 4 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-placeholder14.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-placeholder15.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-placeholder16.C
> >
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 3b2106dd3..479b2a5bd 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -31253,6 +31253,19 @@ do_auto_deduction (tree type, tree init, tree
> > auto_node,
> > full_targs = add_outermost_template_args (tmpl, full_targs);
> > full_targs = add_to_template_args (full_targs, targs);
> >
> > + int want = TEMPLATE_TYPE_ORIG_LEVEL (auto_node);
> > + int have = TMPL_ARGS_DEPTH (full_targs);
> > +
> > + if (want < have)
> > + {
> > + // if a constrained auto is declared in an explicit specialization
> > + gcc_assert (context == adc_variable_type || context == adc_return_type
> > + || context == adc_decomp_type);
> > + tree trimmed_full_args = get_innermost_template_args
> > + (full_targs, want);
> > + full_targs = trimmed_full_args;
> > + }
> > +
> > /* HACK: Compensate for callers not always communicating all levels
> > of
> > outer template arguments by filling in the outermost missing levels
> > with dummy levels before checking satisfaction. We'll still crash
> > @@ -31260,11 +31273,10 @@ do_auto_deduction (tree type, tree init, tree
> > auto_node,
> > these missing levels, but this hack otherwise allows us to handle a
> > large subset of possible constraints (including all non-dependent
> > constraints). */
> > - if (int missing_levels = (TEMPLATE_TYPE_ORIG_LEVEL (auto_node)
> > - - TMPL_ARGS_DEPTH (full_targs)))
> > + if (want > have)
> > {
> > - tree dummy_levels = make_tree_vec (missing_levels);
> > - for (int i = 0; i < missing_levels; ++i)
> > + tree dummy_levels = make_tree_vec (want - have);
> > + for (int i = 0; i < want - have; ++i)
> > TREE_VEC_ELT (dummy_levels, i) = make_tree_vec (0);
> > full_targs = add_to_template_args (dummy_levels, full_targs);
> > }
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder14.C
> > b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder14.C
> > new file mode 100644
> > index 000000000..fcdbd7608
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder14.C
> > @@ -0,0 +1,19 @@
> > +// PR c++/114915
> > +// { dg-do compile { target c++20 } }
> > +
> > +template<typename T>
> > +concept C = __is_same(T, int);
> > +
> > +template<typename T>
> > +void f() {
> > +}
> > +
> > +template<>
> > +void f<int>() {
> > + C auto x = 1;
> > +}
> > +
> > +int main() {
> > + f<int>();
> > + return 0;
> > +}
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder15.C
> > b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder15.C
> > new file mode 100644
> > index 000000000..b4f73f407
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder15.C
> > @@ -0,0 +1,15 @@
> > +// PR c++/114915
> > +// { dg-do compile { target c++20 } }
> > +
> > +template<typename T, typename U>
> > +concept C = __is_same(T, U);
> > +
> > +template<typename T>
> > +int x = 0;
> > +
> > +template<>
> > +C<double> auto x<double> = 1.0;
> > +
> > +int main() {
> > + return 0;
> > +}
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder16.C
> > b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder16.C
> > new file mode 100644
> > index 000000000..f808ef1b6
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-placeholder16.C
> > @@ -0,0 +1,33 @@
> > +// PR c++/114915
> > +// { dg-do compile { target c++20 } }
> > +
> > +template<typename T, typename U>
> > +concept C = __is_same(T, U);
> > +
> > +template<typename T>
> > +struct A
> > +{
> > + template<typename U>
> > + void f() {
> > + }
> > +};
> > +
> > +template<>
> > +template<>
> > +void A<int>::f<int>() {
> > + C<int> auto x = 1;
> > +}
> > +
> > +template<>
> > +template<typename U>
> > +void A<bool>::f() {
> > + C<int> auto x = 1;
> > +}
> > +
> > +int main() {
> > + A<bool> a;
> > + a.f<char>();
> > + A<int> b;
> > + b.f<int>();
> > + return 0;
> > +}
> > --
> > 2.45.0
> >
> >
>
